In general, in an electronic apparatus formed with two or more connected casings, a flexible printed circuit (hereunder referred to as an FPC) is used as a wiring for electrical connection between the casings.
For example, in an electronic apparatus such as a sliding-type mobile phone in which two casings slide mutually with respect to one another, wiring formed with an FPC is generally used. Here, the wiring to be applied to a sliding-type structure requires horizontal bending within an extremely narrow space in the height direction (conventionally 3 mm) between the casings of the sliding hinge, and flexing resistance for approximately 10,000 or more bending cycles. The FPC is used because it has a high level of bendability even in a narrow bending space.
However, in order to further reduce the thickness of electronic apparatus, such as a mobile phone, there is commercially available a sliding hinge having an approximately 2 mm space in the height direction between the casings, to be used in sliding-type electronic apparatus.
In such a thin sliding hinge, as shown in FIG. 5, an FPC 103 is arranged on sides 101a and 102a, which are outer surfaces of the casings, along the outsides of casings 101 and 102, rather than being bent in the height direction H of an inner space between the casings 101 and 102 of a sliding hinge 100. While thereby ensuring a minimum bend radius required for bending the FPC, there has been a problem in that it is difficult to further reduce the thickness of the entire sliding unit including the sliding hinge and the FPC used as a wiring for electrical connection.
Moreover, functionality and performance of electronic apparatuses such as mobile phones are increasingly improving, and consequently improved transmission characteristics and noise resistance characteristics are being required in the electrical connection wiring. However, the FPC has a disadvantage of having a poor noise resistance since a plurality of signal lines are fixed by a resin film or the like, and each of the signal lines is therefore not shielded.
Consequently, to replace the FPC, micro-coaxial cables, which have excellent transmission characteristics and noise resistance characteristics, are used. However, micro-coaxial cables have poorer flexing compared to the FPC, and application thereof is therefore limited to: a so-called clamshell type open/close structure shown in FIG. 6A; a so-called jack-knife type rotation structure shown in FIG. 6B; and a so-called twist type biaxial structure shown in FIG. 6C that performs rotation as well as opening/closing. In contrast, in a sliding-type electronic apparatus as shown in FIG. 6D, micro-coaxial cables can not be applied as a simple form of replacement of the FPC.
On the other hand, JP 2007-036515 discloses a coaxial cable connecting structure that uses coaxial cables that can be applied to a sliding-type electronic apparatus. That is to say, the coaxial cable connecting structure disclosed in patent document 1 is such that inter-substrate wiring between two slidable substrates is configured with a plurality of coaxial cables, these coaxial cables are bound at both end sections thereof, and a portion of the intermediate section that is not bound is accommodated as a surplus length between the substrates. In this case, the coaxial cables of the intermediate section are not bound, and therefore each of the coaxial cables can be freely bent, and mechanical reliability of the inter-substrate wirings can be ensured.
However, in this coaxial cable connecting structure disclosed in JP 2007-036515, the coaxial cables bend in the height direction between the substrates as mentioned above. Therefore, there is a need for ensuring a space in the height direction between the substrates so as to ensure a bending radius of the coaxial cables. Consequently, it has been difficult to reduce the thickness of the sliding unit.
For the above reasons there has been a demand for a sliding unit capable of meeting space-saving needs while having excellent transmission characteristics and noise resistance characteristics, particularly for electronic apparatus having two casings that can freely mutually slide on each other.